Process for vacuum distillation of hydrogen peroxide



J. MERCIER 2,124,257

GEN PEROXIDE July 19, 193s.

PROCESS FOR VACUUM DISTILLATION OF HYDRO Filed Aug. 12, 1955 Invenfor.-Y

Patented July 19,` 1938 UNITED STATES PATENT ori-ICE- PROCESS `OR VACUUMDISTILLATIONOF HYDROGEN PEROXIDE Jean Mercier, NeuiilysurSeine,' FranceApplication .August 12,1935, serial No.'s5;s9s

y i' In France August 21, 1934 1 claim. (ci. 20a- 52) f The object ofthe present invention is aprocess 'forthe vacuum distillation of easilydecomposable liquids, vtogether with an apparatuslto perform thefsame.

This operation'v has always encountered serious dicultiesin practise. Inparticular it has always been found extremely. difiicult to obtainhydrogenperoxidc by vacuum distillation, when y starting from aqueoussolutions of compounds containing active oxygen, due chiefly to the facility with which hydrogen peroxide decomposes in the presence-oflperacids The fact that .the vapour pressure of hydrogen peroxide islower than that of `water .also causes These have necessitated main-rgrave diiiculties. ytaining an optimum .ratio between the'quantities ofwater and hydrogen peroxide to be evaporatedv simultaneously. On theother hand .it is very important to prevent the solidication oi' thereagents owing to the evaporation of water proceeding too far.

In the processes hitherto knowmin which the liquid to be distilled issucked through the evaporator by means of vacuum, and its quantityregulated by means of injectors, cocks or capillary tubes, theconditions prevailingin the evaporator are always irregular.These'drawbacks are particularly applicable to the working of large industrial units .formed of a great number of evaporating tubes.

The .present invention consists in a process of I l evaporation suchthat the same degree of vacuum is maintained at every point in theapparatus, all the parts of .which (as for instance feed-tanks,

. evaporators, collecting vessels etc.) are connected 'to the samevacuum pipe line. ,v By this means the process is carried out in such amanner that the evaporator throughout the whole vapparatus is alwaysuniform..

In the preferred manner of putting the invention'into execution, themovement of the liquid in the apparatus is not obtained as formerly byapplying a difference ofv `pressure between the inlet and the outlet,but by employing a difference of temperature. To eifect this one employsa system of communicating vessels, one of which is a reservoir of anydesired shape and capacity,

the otherV being one or more heated tubes. The difference in temperaturethusA established between the part of the apparatus which is heated andthe part not heated results in imparting a movement to the liquid of anydesired speed simply by regulating the temperature of the hot tube ortubes which are situated between the feed-'tank and the evaporator.'I'his speed is best Vbeing'joined to the same vacuum piping c.

regulated to coincide with that which will give sulcient bubbles ofsteam t'o cause the solution to enter the evaporator in the form of anemullsion and not in the form of a liquid layer, thus in turn causingthe entire s uriace of the evaporating '5 tubes to be filled with asmall quantity of solution. According tothe invention one maintainsuniform conditions in the evaporator by maintaining the same reducedpressure atkthe inlet and the outletof the said evaporator, byemployl0ing a speed for the circulation of the solution which isindependent ofthe suction by vacuum, c and lastly by maintaining` the physicalconditions ofthe solution homogeneous. 'I'he apparatus for putting thepresent invention into execution con- 15 sists essentially of anevaporator lof any desired number of tubes placed in any desiredposition.

The following working examples will serve to y make perfectly plain thepreferred methods of putting the invention into execution. y 20 Fig.y 1represents the main outlines of an apparatus according to the invention.A

Fig. 2 .represents the drawingoi? a lportion of "I .-the rate of feed;consisting of the vessel eand ia series of tubespg. A constant level ismaintained in the vessele by any desired' means, for example the vesselmay be constructed on Mari'- 40 ottes principle with the addedpeculiarity that the tube which dips into the vessel is connectedthrough a flexible connection to the vacuum pip-'- ing so that aregulation of the level in vessel e may b e obtained by modifying theheight of the 45 tube in the vessel. y

As soon as onecommences to heat the tubes g the liquid which is at acertain height begins to ascend'and the emulsion enters the evaporator,The vapour separates from the liquid in the vessel 50 i, and then passesthrough piping k and the refrigerator l to the receivers m where thehydrogen peroxide is collected. The residual liquid flows from thevessel i into the receiver o, connected to the vacuum system operatingthe whole plant. 55

` are three exits for the vapour.

In Fig. 2 the tube g destined to produce thev circulation of the liquidis shown joined to the evaporating tube by an elbow q, but the con'-necting tube q can equally well be straight, or again be so formed thattube q and h are in one piece, the vacuum being applied both at theinlet and outlet of this single tube. At the same time it is consideredgenerally preferable that the two tubes, one for producing thecirculation and the other for the distillation, should be separate, as ithis increases the ease with which they can be maintained at diierenttemperatures.

The present yinvention lends itself particularly well to distillation inwhich the vapour is eliminated at two or more separate points in theevaporator. This manner of working has the advantage of withdrawing thevapour formed away from the zone of heat, and out of Contact with thesolution.

As a result of the desired pressure under which the apparatus is workingbeing identical at all points and the speed of circulation of thesolution being regulated by the heat applied, one always obtains aregular distillation with a high yield in the diierent steps of thisoperation.

In Fig. 3 an apparatus is shown in which there The liquid coming fromthe feed-tank b passes through a first heating tube and a firstcondenser, exactly as in the apparatus outlined in Fig. l. .After havingpassed out through the separating vessel i the vapour passes through thepiping c to the refrigerator, while the liquor enters the second stageof the evaporation through piping n and a second heating tube g. Thissecond stage of evaporation is then followed by a third or even furthersimilar stages, each with a. similar lay-out. Finally after the lastseparating vessel the liquid is sent to the receiver connected to thevacuum piping.

It will `be seen that in all the above described embodiments the vacuumhas absolutely no eifect upon the movement of the liquid by reason A ofthe fact that all of the vessels, for instance,

b, e, y, i, o and m are connected to the vacuum c. Accordingly the sameabsolute pressure exists inthe entirety .of the arrangement and noeffect of pressure or lack of pressure can play any. part in order tocause a displacement of the liquid.

Thus the displacement of the liquid is produced by the sole effect ofthe temperature to which the tube g is subjected.

Having now particularly 4described and ascertained the nature of my-invention and in what manner the same is to be performed, I declarethat what I claim is:

Process for the preparation of hydrogen peroxide by vacuum distillationof solutions containing active oxygen, which comprises passing thesolution to be distilled from a. feed tank through ascending tubes' intoa tubular evaporator, the ascending tubes being heated in such amanner-that a. continuous movement of the liquid to be distilled fromthe feed tank into the tubular evaporator is engendered solely by theyaction o! the heat diierence between the feed tank and the ascendingtubes, all these parts, as well as the rest of the apparatus beingthroughout subjected to substantially the same degree of reducedpressure, th'e elements at the two ends or! the apparatus, namely, thereceiver and the feed tank, being for this purpose connected separatelyand directly to the same vacuum system.

, JEAN MERCIER.

